Use of Plackett-Burman design for rapid screening of several nitrogen sources,growth/product promoters,minerals and enzyme inducers for the production of alpha-galactosidase by Aspergillus niger MRSS 234 in solid state fermentation system

Five sources of nitrogen, six minerals, six enzyme inducers and one each of growth as well as product promotors were screened by Plackett-Burman design, consisting of a total of 20 experiments for the above 19 sources/categories of medium ingredients, for their effect on the production of alpha-galactosidase by Aspergillus niger MRSS 234 in solid state fermentation system. The enzyme production was recorded from 2 to 5 days of fermentation. Data on enzyme titres was analysed by compatible analysis to obtain regression coefficients and t-ratios. Among the nitrogen sources, urea contributed positively to enzyme production and its effect increased with the fermentation time, in contrast to negative effect of all the ammonium salts used. Corn steep liquor, citric acid and legume seed flours showed significantly positive effects on enzyme production, though lactose showed negative effect upto 3 days of fermentation and then turned positive but not significantly. Calcium chloride and ferrous sulphate showed considerable negative effect, in contrast to mixed effect by other mineral salts studied. Among the legume seed flours, guar and French bean flours showed larger positive effects. The studies allowed the selection of urea, corn steep liquor, guar flour, soy bean flour and citric acid as most promising sources/categories for further optimization studies based on the effects as well as their trend with fermentation time. The use of Plackett-Burman design for rapid screening of large number of nutrients, in a very small number of experiments, for reliable short-listing of a few of most effective sources/categories for further optimization, has been scarce in submerged fermentation and never attempted earlier in solid state fermentation system.Authors are thankful to Dr. S. R. Bhowmik, Director of the institute for interest in the work. M. R. S. Srinivas thanks Council of Scientific and Industrial Research, New Delhi, for the award of junior research fellowship.     

Faster induction of photosynthesis increases biomass and grain yield in glasshouse-grown transgenic Sorghum bicolor overexpressing Rieske FeS

Sorghum is one of the most important crops providing food and feed in many of the world's harsher environments. Sorghum utilizes the C₄ pathway of photosynthesis in which a biochemical carbon-concentrating mechanism results in high CO₂ assimilation rates. Overexpressing the Rieske FeS subunit of the Cytochrome b₆f complex was previously shown to increase the rate of photosynthetic electron transport and stimulate CO₂ assimilation in the model C₄ plant Setaria viridis. To test whether productivity of C₄ crops could be improved by Rieske overexpression, we created transgenic Sorghum bicolor Tx430 plants with increased Rieske content. The transgenic plants showed no marked changes in abundances of other photosynthetic proteins or chlorophyll content. The steady-state rates of electron transport and CO₂ assimilation did not differ between the plants with increased Rieske abundance and control plants, suggesting that Cytochrome b₆f is not the only factor limiting electron transport in sorghum at high light and high CO₂. However, faster responses of non-photochemical quenching as well as an elevated quantum yield of Photosystem II and an increased CO₂ assimilation rate were observed from the plants overexpressing Rieske during the photosynthetic induction, a process of activation of photosynthesis upon the dark–light transition. As a consequence, sorghum with increased Rieske content produced more biomass and grain when grown in glasshouse conditions. Our results indicate that increasing Rieske content has potential to boost productivity of sorghum and other C₄ crops by improving the efficiency of light utilization and conversion to biomass through the faster induction of photosynthesis.     

Internalization of insulin and its receptor in the isolated rat adipose cell. Time-course and insulin concentration dependency

The time-course and insulin concentration dependency of internalization of insulin and its receptor have been examined in isolated rat adipose cells at 37 degrees C. The internalization of insulin was assessed by examining the subcellular distribution of cell-associated [125I]insulin among plasma membrane, and high-density (endoplasmic reticulum-enriched) and low-density (Golgi-enriched) microsomal membrane fractions prepared by differential ultracentrifugation. The distribution of receptors was measured by the steady-state exchange binding of fresh [125I]insulin to these same membrane fractions. At 37 degrees C, insulin binding to intact cells is accompanied initially by the rapid appearance of intact insulin in the plasma membrane fraction, and subsequently, by its rapid appearance in both the high-density and low-density microsomal membrane fractions. An apparent steady-state distribution of insulin per mg of membrane protein among these subcellular fractions is achieved within 30 min in a ratio of 1:1.54:0.80, respectively. Concomitantly, insulin binding to intact cells is associated with the rapid disappearance of approx. 30% of the insulin receptors initially present in the plasma membrane fraction and appearance of 20-30% of those lost in the low-density microsomal membrane fraction. However, the number of receptors in the high-density microsomal membrane fraction does not change. This redistribution of receptors also appears to reach a steady-state within 30 min. Both processes are insulin concentration-dependent, correlating with receptor occupancy in the intact cell, and are partially inhibited at 16 degrees C. While the steady-state subcellular distributions of insulin and its receptor do not correlate with that of acid phosphatase, chloroquine markedly increases the levels of insulin associated with all three membrane fractions in apparent proportion to the distribution of this lysosomal marker enzyme activity, without more than marginally potentiating insulin's effects on the distribution of receptors. These results demonstrate that insulin, initially bound to the plasma membrane of the isolated rat adipose cell, is rapidly translocated by a receptor-mediated process into at least two intracellular compartments associated with the cell's high- and low-density microsomes. Furthermore, insulin simultaneously induces the translocation of its own receptor from the plasma membrane into the latter compartment. These translocations appear to represent the internalization and partial dissociation of the insulin-receptor complex through insulin-induced receptor cycling.     

Relationship of Cob characters with Grain Morphology in Maize (Zea mays,Poaceae)

Twenty varieties of maize (Zea mays, Poaceae) were studied through 11 attributes in three to seven randomly selected plants of each variety with a view to understanding the effect of cob characters on technologically desirable grain qualities. Canonical discriminant analysis showed thatproductivity (determined by total grain weight/cob, cob diameter and average grain weight) was the most discriminating among varieties followed by round grains fraction (represented by whole top and middle flat grains, number of rows and grain count/surface area), middle flat grains (composed of middle flat grains and grain count/surface area) and shape of the cob (determined by shape index, total grain weight/cob and cob diameter), which accounted for 35.1, 18.3, 12.2, and 9.8% of the total variance, respectively. In the light of these results, tentative norms have been suggested to evolve maize varieties of superior technological properties and yet retain high productivity. A cylindrical cob of large diameter with highest number of grains/area and smallest possible number of rows together constituted an ideal combination to achieve the objectives. Such possibilities in the light of available information are discussed.     

A thrombin receptor in resident rat peritoneal macrophages.

Resident rat peritoneal macrophages possess 6 x 10(2) high-affinity binding sites per cell for bovine thrombin with a Kd of 11 pM, and 7.5 x 10(4) low-affinity sites with a Kd of 5.8 nM. These binding sites are highly specific for thrombin. Half-maximal binding of 125I-labeled bovine thrombin is achieved after 1 min at 37 degrees C, and after 12 min at 4 degrees C. The reversibly bound fraction of the ligand dissociates according to a biexponential time course with the rate constants 0.27 and 0.06 min-1 at 4 degrees C. Part of the tracer remains cell-associated even after prolonged incubation, but all cell-associated radio-activity migrates as intact thrombin upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The bound thrombin is minimally endocytosed as judged by the resistance to pH 3 treatment, and the receptor does not mediate a quantitatively important degradation of the ligand. The binding is not dependent on the catalytic site of thrombin, since irreversibly inactivated thrombin also binds to the receptor. 125I-labeled thrombin covalently cross-linked to its receptor migrates in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a Mr 160,000, corresponding to an approximate receptor size of Mr 120,000.     

A novel baker's yeast mediated C-C bond cleavage reaction

Summary A novel baker's yeast mediated C–C bond cleavage reaction was observed during the biotransformation of dimethone derivative of thiophene-2-carboxaldehyde (II) to give the product 2-(2-thienyl methyl)-5,5 dimethyl cyclohexa 1,3-dione (III) in 47% yield.     

Age-related motor and catecholomine alterations in mice on levodopa supplemented diet

Old mice reared on regular diet show reduced motor activity, decreased basal adenylate cyclase, and increased MAO activities compared to adults. Brain DDC and COMT activities, DA, NE levels and DA-stimulated adenylate cyclase remained unchanged. By contrast, mice fed levodopa for life did not develop decreased motor activity with aging, lived about 50% longer, had slightly elevated whole brain DA and NE levels and failed to develop the expected rise in MAO activity with aging. Levodopa did not alter the number of dopaminergic and muscarinic cholinergic receptors or the adenylate cyclase activity in the striatum during aging. On levodopa, hepatic and renal DA, dopa, and HVA increased but the latter two returned to basal levels by mid life. In liver, DDC was unchanged but MAO tended to be higher in levodopa-fed mice. Thus, motor impairment is an age-related phenomenon in mice associated with selective alterations in brain dopaminergic systems, which may be prevented by dietary levodopa. Extracerebral tissues, through possibly adaptive metabolic mechanisms, play a significant role in regulating brain catecholamines during chronic administration of large doses of levodopa.